Clutch drive mechanism for poweroperated screw drivers and the like



E. H. SHAFF CLUTCH DRIVE MECHANISIVI FOR POWER OPERATED SCREW DRIVERS AND THE LIKE Origlnal Flled Jan 2 1947 Aug. 14, 19.51

n bw om Patented Aug. 14,- 1951 CLUTCH DRIVE MECHANisM Eon- POWER-g OPERATED SCREW naive-asl AND THE LIKEV Ernest H. shan, spring Lake, assignorjto Keller Tool Company, Grand Haven, Mich., a `corporation of Michigan original application January 2,1947, serial. Nc.

719,803; Divided and this. application June 2 1948, Serial N0; 30,696

1 Claim. (CL 7b-798)" The invention relates to portable power driven tools such as screw" drivers and nut runners, and it has for its primary object the provision in suc-h la tool of a combined speed reduction and friction slip clutch drive between the motor and the tool spindle with means of simple and advantageous construction for adjusting the presvsure between the driving and driven members of the clutch.

Other objects' and advantages of the invention will become aparentfrom the following detailed description taken in connection with the accompanying drawings, in which:

'Figure l is a longitudinal sectional view through a tool having an adjustable drive clutch embodying my invention, the rear end portion of the tool being shown in elevation.

Fig. 2 is a fragmentary pla-n view partially in section of the yclutch adjusting means.

Figs. 3V and 4 are respectively transverse sectional views taken approximately inv the" lines 3-3 and 4-4 of Fig., 1.

As illustrated in the" drawings, the exemplary form.Y of the invention is shown embodied in a portable pneumatic screw driver comprising a generally clindrical main casing III having a rotary pneumatic motor II for driving a spindle I2 through the medium of a drive mechanism including a friction slip clutch I3. In the embodiment shown the front end of the spindle I2 is constructed for driving engagement with a screw driving bit I4.

The tool spindle I2 is journalled in a spindle housing 54 of smaller diameter than and projecting from the main casing I0. Herein the spindle is in the form of a hollow shaft in axial alinement with the tubular drive shaft 2B and having its outer end shaped to form jaws 48 to loosely hold the bit I4 while permitting the passage of air about the latter member for a purpose which will presently appear. The forward end of the s-pindle is journalled in a sleeve 55 rigid with the spindle housing and forming a forward extension thereof.

The driving connection between the motor II and the spindle I2 is of a character such as to permit slippage between the driving and driven members when a predetermined load is applied to the spindle. In the present instance I have shown, for purposes of illustration, a driving connection in the form of a combined clutch and speed reducing mechanism disposed in the 2 tary relation on a spider 511 rigid with' the spindle IZ and coacting'lwith a cone-shaped drive member 5a' rigid with the drive shaft `2 n: The rollers areV journalled ori-"pins" '60 projecting axially toward the motor from" the spider 5'I.A As the rollers are caused' to rotate' about'th'ei'r respective axes by" contact with the drive' cone' they are simulaneously Caused to roll on an internal inclined surface 6I on the sleeve 2'I',V the latter member being concentric with the drive cone.

An important feature of' myr invention resides in the provision of mea-ns' conveniently accessible from" the exterior of'the tool' for varying the* frictionalpressurebetween the drive member and the driven member of the drive mechanism. In 'this` instance, a compression spring 62' encircling?thespindle I2 is interposed between an adjustable abutment or'col-lar 63 encircling the spindle, and a fixed abutment such as a ball thrustY bearing' 64; The force exerted by the-spring is'transmitte'dfto the' spider 51 through the thrust bearing' 634, thereby urging the rollers 5G into frictional' engagement with the tapered surfaces" of the drive cone 58 and the stationaiy sleeve 21.

To adjust the frictional pressure between the surfaces of the frictionally engaged members of the clutch mechanism, the tension of the spring urging the clutch members into engagement may be changed by varying the axial position of the collar 63. For this purpose, I provide means including a sleeve or ring 65 conveniently accessible from the exterior of the tool. The ring encircles the outer end of the spindle housing and one end thereof abuts radial lugs 6B rigid with the collar 53 and projecting through longitudinally extending slots 61 in the spindle housing 54. At its other end the ring is constructed to form a nut 69 screw threaded upon the sleeve 55. It will be seen that by turning the ring the position of the collar 63 may be varied thereby changing the tension of the spring.

As herein shown. the forward end of the tool is constructed to provide a suction-operated nder for receiving and holding a screw or other threaded element. Herein the finder is in the form of a tube 8| encircling the bit I4 and communicating by way of a passageway 19 with a suitable suction producing means (not shown) forming no part of the present invention. Ex tending through the passage 'I9 is a rod 'I0 for the actuation of a valve (not shown) controlling the operation of the motor II.

The tube 8| is slidably mounted in a tapered nosepiece 82 threaded on the sleeve 55, and one end of the tube has an annular ange 83 which abuts a shoulder 84 on the interior of the nose- =piece to prevent withdrawal therefrom. (The other end oi' the tube is formed to receive roundheaded screws more readily.) Normally, the outer end of the tube is forced to protrude beyond the end of the nosepiece by a compression spring 86. The latter encircles the bit and is interposed between the flange 83 and an abutment in the form of a collar 81 encircling the bit, urging the flange into engagement with the shoulder 84. The collar 81 additionally serves to prevent withdrawal of the bit from the tool. Thus it provides a stop for engagement by a shoulder 88 on the shank of the bit I4.

In the operation of the tool the iinder is inserted into a container having a supply of screws and upon contact with the head end of the screw the suction at the finder end of the tool picks up and holds the screw in the proper position (Fig. 1). With the screw thus held applied to the work endwise pressure is applied to the tool, causing the nder to telescope into the nosepiece 82, thereby bringing the bit into engagement with the head of the screw as shown in Fig. 2. Additionally, pressure on the nder urges the rod 19 axially rearward to start the motor.

When the driving torque on the screw has exceeded a predetermined maximum, the clutch drive I3 will slip so that the tool spindle will come to rest. The amount of torque to be applied to `the screw can be quickly and easily changed by drivingly connecting the same, said drive mechanism including a driving element rigid with said shaft and having an outer conical surface thereon, a stationary ring element having a conical inner surface coaxially disposed with respect to said driving element, said inner surface having an equal and opposite slope with respect to the outer surface of the driving element, planet elements disposed between said sun and ring elements and presenting conical outer surfaces complementary to said surfaces of the driving and ring elements for engagement therewith, a carrier rigid with said spindle and rotatably supporting said planet elements, an abutment mounted on said housing, a compression spring interposed between said carrier and abutment and operative to urge said planet elements into engagement with said driving and ring elements, and means for adjusting the position of said abutment to vary the degree of compression of said spring whereby the pressure between the engaged surfaces of the driving ,ring and planet elements is altered.

ERNEST I-I. SHAFF.

REFERENCES CITEDA The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 622,207 Collins Apr. 4, 1899 726,461 Rennerfelt Apr. 28, 1903 1,425,172 Cameron-Cowburn Aug. 8, 1922 1,545,243 Fletcher July 7, 1925 1,642,346 Uytjens Sept. 13, 1927 1,662,681 Lindner Mar. 13, 1928 2,176,928 Short Oct. 24, 1939 2,198,921 Shaff Apr. 30, 1940 2,306,475 Wahl Dec. 29', 1942 2,315,486 Mulder Apr. 6, 1943 FOREIGN PATENTS Number Country Date 530,443 Germany July 29, 1931 

